A lampholder assembly of the type described above is known from European patent specification 0.151.598. That publication discloses in particular a lampholder assembly of which the ballast and the lampholder module proper can be assembled readily, owing to electric wiring built into the lampholder module. Optionally, the support part of the lampholder module can support two lamp parts, as is explained with reference to for instance FIGS. 4 and 5 of the European patent specification mentioned.
In practice, ballast and lampholder module will be incorporated in a larger whole, the fitting, which larger whole must be suitable to be built in or affixed. Such a construction often comprises a plurality of parts--namely, the component to be built in or affixed itself, containing the lampholder module and the ballast, and a covering member. The part that contains the electric components and connections must satisfy certain safety requirements. The quality-control institute designated by the electricity companies (KEMA in the Netherlands), is particularly concerned with the quality-control of said part and tends not to pay any attention to the covering part, which does not comprise any electric components or connections. Because in known constructions the lampholder module is often mounted on a part of the fitting and the ballast therebelow, a large part of that fitting (which term includes the entire "case" or "box") is subject to the safety requirements referred to above. Moreover, building in or affixing such constructions is laborious and time-consuming.